A C2-C6 fluorine-containing compound, for example, perfluorohexanoic acid (PFHA) has a solubility in water of about 20% at normal temperature, which is about 100 times of the solubility of perfluorooctanoic acid (PFOA) in water. Therefore, the adsorption rate of general active carbon, for example, general-purpose active carbon for waste water which was conventionally used is 5% or less at normal temperature and pH 7.
It was difficult to highly adsorb the C2-C6 fluorine-containing compound, which has high solubility in water, with using the conventional active carbon having a specific surface area of 1,000 m2/g or less. Such adsorption method was associated with problems of cost.
Patent Document 1: JP-A-09-315809